CAR SCIENCE | We look at what makes the American V8 great

Gerrit Burger tracks the rise and rise of the iconic American V8 motor

26 July 2019 - 12:41 By Gerrit Burger
A Chevrolet small-block V8 engine.
A Chevrolet small-block V8 engine.
Image: Supplied

Here we are, looking at the heart of an engine. On the left-hand side is one bank of four cylinders, the other bank being on the opposite side, with a 90-degree angle between the two banks. Thus it is known as a 90-degree V8. On the front of the casting are two big, round openings, the lower one for the nose of the crankshaft to poke through so that various drive pulleys and cogs can be mounted on it, the upper opening for the camshaft to go through.

The camshaft will be driven by chain from the crankshaft and its lobes (“cams”) will operate the pushrods, which make the rockers in the cylinder head (not shown) rock to and fro as they open the inlet and exhaust valves in the head. This is called a cam-in-block engine or pushrod engine.

The machined openings in the red areas on either side of the camshaft opening will be blanked off with welch plugs, to which we shall return later. The displacement of this engine is roughly 5,7 litres, which for the Yanks is 350 cubic inches, a magic number in the history of small-block Chevys.

But this is merely the bare-bones technical data. The real beauty of this picture lies in the incredible amount of accumulated experience and know-how required to pour a mass of molten iron into this complex shape in a single operation.

Casting a straight-four engine block is already a tricky operation; casting a V8 block is a veritable tour de force. When Henry Ford wanted to produce an affordable V8 engine to compete with Chev’s straight-six, he had to find a way to cast the V8 block in one piece.

Until then, V8 engines were built up from separate castings for each bank and for the crankcase (the bottom part of the engine where the crankshaft lives), which were then machined, prior to being bolted together to form the complete block.

This was too expensive and time-consuming for the low-cost, mass-market car which Ford had in mind. No, the engine would have to be a monobloc (one-piece) casting. Industry “experts ”, aware of the formidable difficulties involved, shook their heads and declared this to be impossible, but the word impossible didn’t appear in Ford’s dictionary.

He assembled a special team of engineers and technicians who worked, in seclusion, and with Ford spending more time among them than in his office, to find a way of casting a V8 block. For more than two years they toiled and failed, and tried again, and failed and learnt, and slowly got it right.

The 1965 Ford Shelby Mustang GT350 was powered by a small-block V8 engine.
The 1965 Ford Shelby Mustang GT350 was powered by a small-block V8 engine.
Image: Michael Cole/Corbis via Getty Images

Standing tall among them was the lanky figure of Charles Sorensen, known forever after at Ford as “Cast Iron Charlie”. By 1932, four years after the Model T was replaced by the Model A, Ford had enough confidence in the casting techniques to launch his V8 model. That “flathead ” (sidevalve) V8 was in production, progressively improved, but in essence unchanged, until 1953.

It made V8 synonymous with Ford in the ’30s, ’40s and early ’50s. In 1955 The General unveiled its own V8 engine, designed under the leadership of another legend in the American automotive industry, Ed Cole. It became known as the Small Block Chevrolet (SBC) engine and had a production run of more than 56 years and a staggering total production figure of more than 100 million engines. The engine in the picture is a descendant of Cole’s SBC.

To appreciate the challenges inherent in casting a V8 engine block, consider that the mould must make provision not only for the two banks of cylinders, with their water jackets, oil galleries, crankshaft supports, mounting points for ancillaries and precisely placed reinforcing ribs and ridges, but, to prevent warping, care must also be taken that no part of the casting will cool faster than another nearby section.

As for the actual process to make iron castings, sand-casting, or a refinement thereof, is the most common method. Basically, this involves first making a pattern of the required shape in wood, metal or plastic, which is then placed in a two-piece moulding box and firmly packed with special sand that is held together by a bonding agent. After the sand has hardened, the moulding box is split open to remove the pattern for re-use.

The box enclosing the “negative” of the casting is reassembled and molten iron, at around 1,400C, is then poured into the cavity and allowed to cool and solidify. Finally, the casting sand is flushed out from the internal cavities of the block through the welch plug openings, after which the blanking plugs can be knocked in. The impurities in the iron and their percentages are critical. The temperature of the molten iron as it enters the mould must be maintained within a very narrow band around the optimum temperature, which has been established by trial.

The Americans had to earn their reputation as the masters of cast iron the hard way. Modern cars often have aluminium alloy engine blocks and these are sometimes produced by “die casting”, where molten metal is forced under high pressure into a mould cavity. But that’s a story for another day.